JP2005333644A - Filter incorporating inductor, duplexer and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small filter employing an air gap type film bulk acoustic resonator which can be manufactured through a simple process. <P>SOLUTION: The filter comprises a substrate having a first port, a second port and a ground port for electrical connection with external terminal formed on the upper surface, at least one first film bulk acoustic resonator formed on the surface of the substrate and connecting the first and second ports in series, at least one second film bulk acoustic resonator being connected in parallel with a coupling node formed between the first and second ports, and at least one inductor for connecting the second film bulk acoustic resonator and the ground port in series. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a filter using a thin film bulk acoustic resonator (hereinafter referred to as “FBAR”), a duplexer, and a method for manufacturing the same. Specifically, the present invention relates to a filter, a duplexer manufactured by assembling an inductor for adjusting resonance characteristics and an FBAR manufactured in a single chip shape in series or in parallel, and a manufacturing method thereof.

  Recently, as mobile communication devices typified by mobile phones are rapidly spread, demands for both small and light filters and duplexers used in such devices are increasing. On the other hand, FBAR is well known as a means suitable for use as such a small lightweight filter. The FBAR can be mass-produced at a minimum cost and can be configured to be small and light. Further, the quality factor (Quality Factor: Q) value, which is a main characteristic of the filter, can be increased, and the filter can also be used in the micro frequency band. In particular, it has an advantage that it can be configured over PCS (Personal Communication System) and DCS (Digital Cordless System) bands.

  In general, the FBAR element includes a resonance part in which a lower electrode, a piezoelectric layer (Piezoelectric layer), and an upper electrode are sequentially stacked on a substrate. The operation principle of the FBAR element is that electric energy is applied to the electrode to induce an electric field that changes with time in the piezoelectric layer, and this electric field is generated in the piezoelectric layer in the same direction as the vibration direction of the resonance part (Bulk). Resonance is generated by inducing an Acoustic Wave).

On the other hand, a ladder-like filter is used as one of the filters using the FBAR element. The ladder filter refers to a band-pass filter that can pass only a signal in a predetermined frequency band by combining a plurality of FBAR elements in series and in parallel and then adjusting the resonance characteristics of each element.
FIG. 1 is a block diagram showing the configuration of a ladder filter according to the prior art in which a plurality of acoustic resonators (Thin Resonators: TFR) are combined in series and in parallel (see Patent Document 1 (US Pat. No. 6,377,136)). According to FIG. 1, the filter includes series acoustic resonators such as TFRs1, s2,.. SN, and parallel acoustic resonators such as TFRp1, p2,. Each series acoustic resonator 11, 12,... N is connected in series between the input end and the output end. On the other hand, each parallel acoustic resonator 21, 22... N connects a connection node (node) and a ground (ground) between the series acoustic resonators 11, 12,.

  FIG. 2 is a graph showing impedance characteristics of series and parallel acoustic resonators included in the ladder filter. According to the figure, the impedance characteristic graph 30 of the series acoustic resonator has frequencies f1 and f2 that are anti-resonance frequency and resonance frequency, respectively, and the impedance characteristic graph 40 of the parallel acoustic resonator has anti-resonance frequencies f3 and f4, respectively. Frequency and resonance frequency. Accordingly, the frequency characteristics of the series acoustic resonator or the parallel acoustic resonator are adjusted so that the anti-resonance frequency f3 of the parallel acoustic resonator matches the resonance frequency f2 of the series acoustic resonator, so that the frequency band f1. It operates as a band-pass filter that passes only signals between f4 and f4. In this case, the resonance frequency of the bandpass filter is f2 (= f3).

In the filter shown in FIG. 1, in order to adjust the frequency characteristics of a series acoustic resonator or a parallel acoustic resonator, the thickness and material of electrodes, piezoelectric films, etc. constituting each acoustic resonator are made different from each other. There must be. Therefore, there is a problem that the manufacturing process is different for each acoustic resonator.
On the other hand, after appropriately combining acoustic resonators having uniform frequency characteristics, an element such as an inductor can be connected to the parallel acoustic resonator to adjust the frequency characteristics of the bandpass filter. However, the volume of the element increases when an external element such as an inductor is connected. Therefore, it is difficult to use in a small communication device such as a mobile phone.

  On the other hand, such a filter can use an element such as a duplexer. The duplexer is an element that transmits and receives signals via one antenna, and generally includes a transmission end filter, a reception end filter, and a filter isolation unit that prevents signal interference between the filters. The transmission end filter is a filter that filters only a signal transmitted to the outside through an antenna, and the reception end filter is a filter that filters only a signal received from the outside. The filter separator may be implemented as a phase shifter that prevents mutual interference so that the phase difference between the frequencies of the transmission signal and the reception signal is 90 °. The phase shifter can usually use a capacitor and an inductor.

Since the duplexer is also an element that uses a filter, there is a problem that the volume increases if the size of the manufactured filter is large. Furthermore, when the manufacturing process of a filter becomes difficult, the problem accompanied by difficulty at the time of manufacture of a duplexer is included.
US Pat. No. 6,377,136

  The present invention has been devised to solve the above-described problems. The object of the present invention is to reduce the size by integrally manufacturing the inductor and the acoustic resonator through a simplified manufacturing process. It is to provide a filter, a duplexer, and a manufacturing method that can be realized.

  In order to achieve the above object, a filter according to an embodiment of the present invention includes a substrate in which a first port, a second port, and a ground port that can be electrically connected to an external terminal are formed on an upper surface; On the surface of the substrate, at least one first thin film bulk acoustic resonator connecting the first port and the second port in series, the first port and the second port At least one second thin film bulk acoustic resonator, one of which is connected to a connection node formed between the second thin film bulk acoustic resonator and the other of the second thin film bulk acoustic resonator and the ground port in series. One inductor.

In this case, any one of the first thin film bulk acoustic resonator and the second thin film bulk acoustic resonator includes a cavity formed in a predetermined region of the upper surface of the substrate, a bottom surface of the cavity, It is preferable that the upper layer space separated by a predetermined distance includes a resonance part formed by a structure in which the first electrode, the piezoelectric film, and the second electrode are sequentially stacked.
Meanwhile, the inductor includes a piezoelectric film laminated on an upper surface of a substrate excluding a region where the cavity is formed, a metal layer laminated in a predetermined coil shape on the upper surface of the piezoelectric film, and the metal More preferably, it includes a connection line that electrically connects the layer and the second thin film acoustic resonator.

  A duplexer according to an embodiment of the present invention includes at least one first inductor, filters a received signal in a predetermined frequency band determined by an inductance of the first inductor, and at least one first inductor. A second filter configured to filter a transmission signal in a predetermined frequency band determined by an inductance of the second inductor, the first filter, and the second filter, and the first filter And a filter isolator for blocking signal inflow with the second filter.

  Preferably, the circuit board further includes a board on which a first port, a second port, and a third port capable of being electrically connected to an external terminal are formed, and each of the second port and the third port is the first filter. And the second port, the first port is connected to the first filter and the filter separator, and the filter separator is connected between the first port and the second filter. preferable.

  Meanwhile, any one of the first filter and the second filter includes at least one first thin film bulk acoustic resonator that connects a predetermined input port and an output port in series, the input port, At least one second thin film bulk acoustic resonator, one of which is connected to a connection node formed between the output port and the other of the second thin film bulk acoustic resonator and a predetermined ground port in series. Preferably, at least one inductor to be connected is included.

Further, the inductor includes a piezoelectric film laminated on an upper surface of the substrate excluding a region where the cavity is formed, a metal layer laminated in a predetermined coil shape on the upper surface of the piezoelectric film, and the metal And a connecting line for electrically connecting the second thin film bulk acoustic resonator.
Preferably, the filter isolation unit is implemented in a form in which at least one capacitor and a coil are assembled, and a frequency phase difference of signals filtered by the first filter and the second filter is 90 °.

  On the other hand, a method for manufacturing a filter according to an embodiment of the present invention includes: (a) a step of laminating a predetermined insulating film on an upper surface of a substrate; and (b) laminating a first metal layer on the insulating film. Patterning to manufacture a plurality of first electrodes, (c) laminating a piezoelectric film on the top surfaces of the plurality of first electrodes and the insulating film, and (d) the piezoelectric film Patterning a second metal layer on the upper surface and patterning to produce a plurality of second electrodes and a predetermined coil-shaped inductor; (e) the first electrode, the piezoelectric film, and the second Manufacturing a plurality of confined film bulk acoustic resonators by etching an air gap by etching a substrate disposed under a region where electrodes are sequentially stacked.

  In this case, the step (e) includes the steps of manufacturing at least one via hole penetrating a predetermined area under the substrate, etching the substrate area using the via hole, and a predetermined package. Bonding a bonding substrate and closing the via hole.

  In the filter according to the present invention, by forming a plurality of FBARs and inductors on one substrate, when adjusting the frequency characteristics during the manufacture of the filter, it is possible to reduce the trouble of performing the steps for each FBAR in different steps. Can do. Further, by manufacturing the inductor and each FBAR on one substrate, it is possible to reduce the size of the element, and at the same time, it is possible to manufacture a duplexer using this filter. In this case, the manufacturing process of the duplexer is simplified by simultaneously manufacturing the filter with the built-in inductor and the filter isolation part, and the duplexer can be manufactured in a small size.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 3 is a block diagram showing the configuration of a filter that combines a plurality of thin film bulk acoustic resonators according to an embodiment of the present invention. According to the figure, a plurality of serial FBARs 110, 120,... M such as FBARs1, s2,... SM, and a plurality of parallel FBARs 210, 220,. .. x, connected in series between m and ground, such as inductors 1, 2,... x. As described above, a plurality of FBARs can be combined in series and in parallel to implement a ladder type filter. Thereby, as shown in FIG. 2, it operates as a bandpass filter that filters only a signal in a predetermined frequency band.

On the other hand, as series and parallel FBARs, an air gap type FBAR including a resonance part having a structure in which a lower electrode, a piezoelectric film, and an upper electrode are sequentially stacked on a substrate and an air gap disposed below the resonance part is used. it can.
The inductors 310, 320,... X are manufactured by laminating a metal material on a substrate in a circular shape or a square shape. The filter shown in FIG. 3 is a filter in which series FBARs 110, 120,... M, parallel FBARs 210, 220 ... m, and inductors 310, 320,. It is. Therefore, an inductor can be realized by using the manufacturing process of each FBAR as it is. That is, in the process of depositing and patterning the upper electrode or the lower electrode, the inductor is manufactured by patterning in a certain coil shape. In addition, a piezoelectric film can be used as an insulating layer that insulates the inductor from the substrate. As shown in FIG. 3, the frequency characteristics on the parallel FBAR side can be adjusted by serially measuring inductors having a predetermined inductance in parallel FBARs 210, 220,. Thereby, it is not necessary to manufacture each FBAR in a different process in consideration of a material used or a thickness.

  FIG. 4 is a cross-sectional view of a portion where the inductor 300 connects one parallel FBAR 200 and the ground 400. The inductor 300 is manufactured on the same substrate 100 as the parallel FBAR 200 and forms a single chip. On the other hand, the inductor 300 is connected to the parallel FBAR 200 and the surround 400 via connection lines 350a and 350b made of a predetermined metal.

  FIG. 5 is a cross-sectional view for explaining the detailed structure of the inductor 300 portion of FIG. According to the figure, metal lines 110 are laminated in a predetermined form on the upper surface of the substrate 100, and the piezoelectric film 120 is laminated on the entire upper surface of the substrate 100 including the metal lines 110. A metal layer is laminated on the upper surface of the piezoelectric film 120 and then patterned into a predetermined form to form the inductor 300 and connection lines 350a and 350b. In this case, the metal layer portion laminated in the coil state operates as the inductor 300. Meanwhile, the metal layer is formed with a connection line 350 connected to the external ground 400 on the upper surface of the piezoelectric film 120. One side 350 a of the connection line is electrically connected to the inductor 300 through the lower metal line 110. As a result, other external elements, that is, the parallel FBAR 200 and the inductor 300 are electrically connected. On the other hand, the other 350 b of the connection line is connected to the ground 400. As shown in FIG. 5, when the inductor 300 is connected in series to the parallel FBAR 200, the inductance of the parallel FBAR 200 is increased by the amount of self-inductance (inductance: L) that the inductor 300 has. The self-inductance of the inductor 300 can be adjusted according to the length and form of the coil, and the frequency characteristics of the filter itself can be easily adjusted.

  On the other hand, although the case where no air gap is formed below the inductor 300 in FIG. 5 is shown, it is also possible to form the air gap by etching the substrate in a predetermined region in order to isolate it from the substrate. In this case, the air gap is manufactured by a method of etching the substrate by introducing an etching solution or etching gas into the lower portion of the substrate through a via hole. FIG. 5 shows the case where the inductor 300 is connected to the parallel FBAR 200. However, when the filter is designed, it can be connected to the series FBAR.

6A to 6E are cross-sectional views for explaining a manufacturing process of a filter according to an embodiment of the present invention. As described above, a plurality of series FBARs and parallel FBARs are required to form one filter. For convenience of explanation, FIGS. 6A to 6E are shown as sectional views for one FBAR and an inductor.
In FIG. 6A, first, an insulating film 510 is deposited on the upper surface of the substrate 500. The insulating film 510 is a portion for electrically separating the metal portion from the substrate 500. Silicon dioxide (SIO ₂ ), aluminum oxide (AL ₂ O ₂ ), or the like is used as an insulating material for forming the insulating film 510. Meanwhile, an RF magnetron sputtering method, an evaporation method, or the like is used as a deposition method for depositing the insulating film 510 on the substrate 500.

  Next, as shown in FIG. 6B, the first electrode 520 is deposited on the upper surface of the insulating film 510 and then patterned to expose a predetermined portion of the insulating film 510. The first electrode 520 is formed using a normal conductive material such as metal. In detail, aluminum (AL), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), titanium (Ti), chromium (Cr), palladium (Pd), molybdenum (Mo), etc. Can be used.

  Next, as shown in FIG. 6C, a piezoelectric film 530 is deposited on the entire surface of the exposed insulating film 510 and the first electrode 520. As described above, the piezoelectric film 530 is a portion that causes a piezoelectric effect that converts electrical energy into mechanical energy in the form of elastic waves. Examples of the piezoelectric material forming the piezoelectric film 530 include aluminum nitride (AlN) and zinc oxide (ZnO).

  As shown in FIG. 6D, the second electrode 540 is deposited on the piezoelectric film 530 and then patterned. In this case, the second electrode 540 remaining on the upper portion of the piezoelectric film 530 provided with the first electrode 520 below forms the resonance part 210 together with the first electrode 520 and the piezoelectric film 530. On the other hand, the inductor 300 is formed by leaving the second electrode 540 in a circular or quadrangular shape on the piezoelectric film 530 other than the portion where the resonance part 210 is formed. On the other hand, the first electrode 520 serves as a connection line that electrically connects the resonance unit 210 and the inductor 300. In addition, the connection line 350 with the ground can be configured using the second electrode 540.

  As shown in FIG. 6E, the air gap 220 is manufactured by etching the substrate 500 below the resonance unit 210. In this case, the via hole 230 penetrating the lower or upper portion of the substrate 500 is manufactured to manufacture the air gap 220. When manufacturing the via hole 230 in the lower portion of the substrate 500, the packaging substrate 550 can be separately bonded to prevent foreign matters flowing in through the via hole. As a bonding method, a direct bonding method in which a temperature is applied, a bipolar bonding method in which a voltage is applied, a bonding method using an adhesive such as an epoxy, or a metal is used. Although there are eutectic bonding methods, direct bonding and bipolar bonding methods are performed at a relatively high temperature stage. Therefore, it is preferable to use an adhesive utilization method or a eutectic bonding method performed at a low temperature stage.

When the air gap 220 is formed, the manufacture of the air gap type FBAR 200 is finally completed. On the other hand, it goes without saying that the substrate gap under the inductor 300 is also etched to produce an air gap.
FIG. 7 is a block diagram showing a configuration of a duplexer 600 (duplexer) according to an embodiment of the present invention manufactured using the filter shown in FIG. As described above, the duplexer is a typical element that uses a band pass filter (BPF). Referring to FIG. 7, a duplexer according to an embodiment of the present invention includes a first BPF 610, a filter separator 620, a second BPF 630, a first port 640, a second port 650, a third port 660, and a ground port 670. .

A filter configured by combining a plurality of air gap type FBARs in series and in parallel from the first and second BPFs 610 and 630 can be used. In this case, as shown in FIG. 3, each filter can use a single chip formed on one substrate up to the inductor.
The first, second, and third ports 640, 650, and 660 are portions that are electrically connected to external elements, and are formed of a conductive material. Each port is connected to the first and second BPFs 610 and 630 and the filter isolation unit 620 using a connection line 680 made of a predetermined metal material.

On the other hand, the ground port 670 shown in FIG. 7 indicates a portion electrically connected to an external ground terminal.
According to the figure, the first port 640 serves to connect an external antenna (shown) to the first BPF 610 and the filter separator 620. If the first BPF 610 is a reception end filter and the second BPF 630 is a transmission end filter, the received signal is not applied to the second BPF 630 but applied to the first BPF 610 for the filter separator 620.

As described above, the filter isolation unit 620 can be configured by a phase shifter (Phase Shifter) in which an inductor and a capacitor are combined. Since the phase shifter makes the frequency shift difference between the reception signal and the transmission signal 90 °, the transmission end filter and the reception end filter can be isolated.
Each of the ports 660, 670, 680, the connection line 680, the filter isolation part 620, etc. shown in FIG. 7 is manufactured collectively on one substrate using the manufacturing process of the first and second BPFs 610, 630. As the manufacturing process, one manufacturing process shown in FIGS. 6A to 6E is used as it is. That is, after the insulating layer 510 is deposited on the upper surface of the single substrate 500, the first electrode 520, the piezoelectric film 530, the second electrode 540, and the like are formed in predetermined forms at the positions of the first BPF 610, the filter separator 620, and the second BPF 630. Can be manufactured at the same time. In this case, the first BPF 610 and the second BPF 630 include an inductor 300 therein, and the frequency characteristics are adjusted by the inductor 300. This eliminates the need to adjust the electrode thickness and the like for each of the FBARs constituting the first BPF 610 and the second BPF 630, thereby simplifying the manufacturing process and incorporating the inductor 300, thereby reducing the volume of the element. The increase can be suppressed.

  Although the preferred embodiments of the present invention have been illustrated and described with reference to the drawings, the protection scope of the present invention is not limited to the above-described embodiments, and the invention described in the claims and equivalents thereof are described. It extends to things.

  The present invention can be used for mobile communication devices such as mobile phones, notebook computers, PDAs, and the like that use small and light filters and duplexers.

It is the block diagram which showed the structure of the ladder (Ladder) type filter conventionally manufactured combining the thin film bulk acoustic resonator. It is the graph which showed the impedance characteristic of the thin film bulk acoustic resonator which comprises a ladder (Ladder type) filter. It is the block diagram which showed the structure of the filter which concerns on one embodiment of this invention. FIG. 4 is a schematic diagram for one thin film bulk acoustic resonator and inductor forming the filter of FIG. 3. FIG. 5 is a cross-sectional view illustrating a detailed configuration of the inductor of FIG. 4. FIG. 4 is a cross-sectional view for explaining a manufacturing process of the filter of FIG. 3. FIG. 4 is a cross-sectional view for explaining a manufacturing process of the filter of FIG. 3. FIG. 4 is a cross-sectional view for explaining a manufacturing process of the filter of FIG. 3. FIG. 4 is a cross-sectional view for explaining a manufacturing process of the filter of FIG. 3. FIG. 4 is a cross-sectional view for explaining a manufacturing process of the filter of FIG. 3. It is the block diagram which showed the structure of the duplexer using the filter which concerns on one embodiment of this invention.

Explanation of symbols

100 Substrate 110, 520 First electrode 200 Thin film bulk acoustic resonator 300 Inductor 350a, 350b Connection line 400 Ground port 120, 530 Piezoelectric film 540 Second electrode 550 Packaging substrate 600 Duplexer 610 First band pass filter 620 Filter isolation part 630 Second bandpass filter

Claims (10)

A substrate having a first port, a second port, and a ground port that can be electrically connected to an external terminal formed on the upper surface;
At least one first thin film bulk acoustic resonator (Film Bulk Acoustic Resonator) connected in series between the first port and the second port on the substrate surface;
At least one second thin film bulk acoustic resonator, one of which is connected to a connection node formed between the first port and the second port;
At least one inductor connected in series between the other of the second thin film bulk acoustic resonator and the ground port;
The filter characterized by including. One of the first thin film bulk acoustic resonator and the second thin film bulk acoustic resonator is
A cavity formed in a predetermined region of the upper surface of the substrate;
A resonance part formed in a structure in which a first electrode, a piezoelectric film and a second electrode are sequentially laminated in an upper layer space separated from the bottom surface of the cavity part by a predetermined distance;
The filter according to claim 1, comprising: The inductor is
A piezoelectric film laminated on the upper surface of the substrate excluding the region where the cavity is formed;
A metal layer laminated in a predetermined coil shape on the upper surface of the piezoelectric film;
A connection line for electrically connecting the metal layer and the second thin film acoustic resonator;
The filter according to claim 2, comprising: A first filter comprising at least one first inductor and filtering a received signal in a predetermined frequency band determined by an inductance of the first inductor;
A second filter comprising at least one second inductor and filtering a transmission signal in a predetermined frequency band determined by an inductance of the second inductor;
A filter isolator formed between the first filter and the second filter and blocking signal inflow between the first filter and the second filter;
A duplexer characterized by including: And further including a substrate on which a first port, a second port, and a third port capable of being electrically connected to an external terminal are formed,
The second port and the third port are connected to the first filter and the second filter, respectively, the first port is connected to the first filter and the filter isolation unit, and the filter isolation unit is the first filter The duplexer according to claim 4, wherein the duplexer is connected between a port and the second filter. Any one of the first filter and the second filter is:
At least one first thin film bulk acoustic resonator connecting in series between a predetermined input port and an output port;
At least one second thin film bulk acoustic resonator, one of which is connected to a connection node formed between the input port and the output port;
At least one inductor connected in series between the other of the second thin film bulk acoustic resonator and a predetermined ground port;
The duplexer according to claim 4, comprising: The inductor is
A piezoelectric film laminated on the upper surface of the substrate excluding the region where the cavity is formed;
A metal layer laminated in a predetermined coil shape on the upper surface of the piezoelectric film;
A connection line electrically connecting the metal layer and the second thin film bulk acoustic resonator;
The duplexer according to claim 6, comprising:   The filter isolation unit is configured in a form in which at least one capacitor and a coil are assembled, and a frequency phase difference of signals filtered by the first filter and the second filter is 90 °. Item 8. The duplexer according to Item 7. (A) laminating a predetermined insulating film on the upper surface of the substrate;
(B) laminating a first metal layer on the insulating film and then patterning to produce a plurality of first electrodes;
(C) laminating a piezoelectric film on the upper surfaces of the plurality of first electrodes and the insulating film;
(D) performing a patterning after laminating a second metal layer on the upper surface of the piezoelectric film, and manufacturing a plurality of second electrodes and a predetermined coil-shaped inductor;
(E) etching a substrate disposed below a region where the first electrode, the piezoelectric film, and the second electrode are sequentially stacked to produce an air gap, thereby forming a plurality of confined film bulk acoustic resonators; Manufacturing steps;
The filter manufacturing method characterized by including. The step (e) includes:
Manufacturing at least one via-hole penetrating a predetermined region under the substrate;
Etching the substrate region using the via hole;
Bonding a predetermined packaging substrate and closing the via hole;
The filter manufacturing method according to claim 9, comprising:

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